My mouse suddenly stopped working with 2.5.73. I am using a Synaptics
Touchpad --
with comes with a Dell laptop. (I will test with an external mouse later).

The SERIO I8042 driver seems to find my mouse, interrupts are firing,
and I enabled
the old /dev/psaux so that userland doesn't see anything different.
Most importantly,
the same config worked with 2.5.72. I noticed that dmesg was slightly
different across
the two versions which suggests that something did change.